It is often desirable to monitor the primary input voltage (power mains voltage) in a mission critical power supply system, such as those used in security and life safety applications. Since the monitoring hardware usually resides in the secondary low voltage side, it is critical to generate an accurate measurement of the primary input voltage from the secondary side of the isolated power supply. The existing approach for obtaining a primary voltage measurement is to use a signal transformer. While this approach is sufficient for many applications, the signal transformer takes up too much space for some applications.